When composing your picture, pay attention to the weather. If it is overcast outside, try to keep the sky out of your picture as much as possible. Black and white pictures are also a good choice if you want to shoot outside on an overcast day. If the weather is nice and sunny, you will get a lot of great pictures, just make sure your subject isn't squinting at the sun.
Make use of the instant feedback you get from a digital camera. The screen on your digital camera can show you the basics of how your photo came out the instant you snap the shot. Learn from your mistakes and take another shot, there's no need to wait for your prints anymore.
One of the key ways to take great photographs is to take lots and lots of them, so buy a large memory card that can hold them all. By increasing the size of the memory card that you use in your camera, you are increasing the number of photos that you can take before changing cards. A large card will also allow you to use RAW format so you can take advantage of the additional flexibility it offers.